1. Technical Field
The present disclosure relates to a method for testing a mask article, and more particularly, to a method for testing a mask article by applying an electrical bias across the mask article and measuring the corresponding current distribution of the mask article.
2. Description of Related Arts
Semiconductor photolithography processes utilize masks for patterning. Conventionally, mask designers manufacture masks according to integrated circuit (IC) designs in semiconductor industries or thin film transistor (TFT) designs for liquid crystal display (LCD) and color filter (CF) designs in photoelectronic industries or printed circuit board (PCB) designs obtained from IC, TFT, LCD, CF, PCB designers/clients. After finishing the masks, the mask designers will provide the IC, TFT, LCD, CF, PCB designers and/or clients with defect maps for showing the locations of mask defects on a corresponding wafer or a photoelectronic substrate (e.g. glass substrate) onto which mask patterns of the masks will be transferred.
A mask defect on a mask is anything that is different from a desired mask pattern and that occurs during the mask manufacturing process. Typically, the above defects on the mask can be inspected, for instance, by scanning the surface of the finished mask with a high resolution microscope or an inspection machine and capturing images of the mask. The next step is determining whether or not the inspected mask is good enough for use in the lithography process. This step can be performed by a skilled-inspection engineer, or by fabrication workers possibly with the aid of inspection software. If there are no defects, or defects are discovered but determined to be within tolerances set by the manufacturer or end-user, then the mask is passed and used to expose a wafer or photoelectronic substrate. If defects are discovered and fall outside tolerances, then the mask fails the inspection, and a decision must be made as to whether the mask may be cleaned and/or repaired to correct the defects, or whether the defects are so severe that a new mask must be manufactured.
As a result of the continuous progression of smaller pattern design, even very small defects in the mask or the mask blanks can negatively affect production yields. For example, the major challenge for Extreme Ultraviolet lithography (EUVL) is how to provide a defect-free mask blank; i.e., how to detect the nano-scale defects on the mask blank. However, the conventional defect detection system cannot meet the precision requirements resulting from the continuous progression of smaller pattern design. Hence, there is a need for a defect detection system that addresses the inefficiency arising from the existing technology.